1. Field of the Invention
The present invention relates to a semiconductor wafer etching apparatus and, more particularly, to an apparatus for etching a semiconductor wafer with a fast atom beam.
2. Prior Art
Semiconductor devices are decreasing in size year by year. Nowadays, highly integrated LSIs, e.g., 16 Mega (M) to 64 M bit memories, are being produced. In the process of producing these semiconductor devices, etching apparatuses are used to etch thin films formed by sputtering, CVD, etc. into desired circuit patterns, Such etching apparatuses are must to be capable of effecting finer etching at a higher reaction rate and with improved selectivity and also must be compatible with wafers having large diameters.
Conventional etching apparatuses of the type described above have heretofore been arranged to etch specimens, e.g., semiconductor wafers, chemically and physically by using charged particles such as those in a plasma or ions. Therefore, the conventional etching apparatuses have disadvantages as stated below.
I. With the etching process that employs a plasma, anisotropic etching cannot be effected because it is impossible to control the direction of incidence of charged particles or active species impinging the substrate surface.
II. When an insulating film such as SiO.sub.2 is etched by using ions, for example, the semiconductor substrate itself may be charged with electricity. There is, therefore, a likelihood that the etching will not proceed, or dielectric breakdown of the insulating film will occur due to the charged substrate.
III. When etching is carried out by using an ion beam, the beam is likely to diverge due to the repulsion between ions, so that it is difficult to maintain the required etching accuracy.
IV. Charged particles are readily affected by a magnetic field or the condition of the atmosphere because of their electrical properties. Therefore, it is difficult to etch semiconductor wafers having large diameters by using charged particles.
In addition, the conventional etching apparatuses of the type described above suffer from the disadvantage that the semiconductor wafer surface may be contaminated by impurities generated from the apparatus or impurities in the atmosphere before, after or during the etching operation.